An Evolved Packet System (EPS) of the 3rd Generation Partnership Project (3GPP) consists of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), a Mobility Management Entity (MME), a Serving Gateway (S-GW), a Packet Data Network Gateway (P-GW), a Home Subscriber Server (HSS), an Authentication, Authorization and Accounting (AAA) server of the 3GPP, a Policy and Charging Rules Function (PCRF) entity, and other supporting nodes, as shown in the EPS box in FIG. 1, wherein the MME is responsible for work related to a control plane such as mobility management, non-access layer signalling processing, and user-mobility-management-context management; the S-GW is an access gateway device connected with the E-UTRAN, forwards data between the E-UTRAN and the P-GW, and is responsible for buffering the data during the paging phase; and the P-GW is a border gateway of the EPS and a Packet Data Network (PDN), and is responsible for functions such as access of the PDN and data forwarding between the EPS and the PDN; wherein as a network deployment is implemented, the S-GW and the P-GW may be arranged together or separately, and may be referred to as Evolved Packet Core (EPC) gateway or integrated service gateway after being arranged together. The PCRF is a Policy and Charging Rules Function entity connected to an Internet Protocol (IP) service network of an operator through a receiving interface Rx to receive service information; moreover, the PCRF is also connected to a gateway device within the network through a Gx/Gxc interface, and is responsible for initiating establishment of an IP bearer, ensuring Quality of Service (QoS) of service data, and performing charging control.
The EPS supports access of a Home evolved NodeB (HeNB, also referred to as a Home NodeB for short in the disclosure), as shown in FIG. 1. The HeNB is a miniaturized low-power base station, which is deployed at indoor locations such as a house, an office, a business building and so on. The HeNB generally accesses a core network of the EPS via a rented fixed network line. In order to guarantee secure access, a Security Gateway (SeGW) is introduced in the core network to perform shielding, and data between the HeNB and the SeGW will be encapsulated with IP Security (IPSec). The HeNB may be directly connected to the MME and the S-GW of the core network via an IPSec tunnel established with the SeGW, or may be connected to the MME and the S-GW via an HeNB GW, i.e., the HeNB GW is an optional network element (NE). At the same time, in order to manage the HeNB, an NE Home eNodeB Management System (HeMS) is introduced. Moreover, a Universal Mobile Telecommunications System (UMTS) supports access of the Home NodeB (HNB). The related technology is similar to that of the HeNB.
The QoS of the fixed network line for access of the H(e)NB (i.e., a blanket term for the HeNB and the HNB) is generally restricted by a contract between an H(e)NB owner and a fixed network operator, therefore when a 3GPP user equipment (UE) accesses the 3GPP core network to access a service through the H(e)NB, the required QoS cannot exceed the contracted QoS of the fixed network line that can be provided by the fixed network operator. Otherwise, the QoS of the service accessed by the UE, in particular a Guaranteed Bitrate (GBR) service, will not be guaranteed. Therefore, for a 3GPP network and the fixed network, a unified control and management mechanism is required to implement admission control of user/connection/service. The solution currently accepted preliminarily by the Organization for Standardization is as shown in FIG. 1 (the case of HeNB). A PCRF, i.e., Policy Control and Charging (PCC) NE of the 3GPP system, is connected to a Broadband Policy Control Function (BPCF) entity of the fixed network via an interface S9* to implement policy interworking and resource management, thus implementing reasonable control and management of a fixed network resource and ensuring preferentially an resource with a high priority for access via the H(e)NB.
As described above, if the fixed network is required to ensure the QoS for the line for access of the H(e)NB, the fixed network is required to locate the fixed network line where the H(e)NB is currently located (referred to as a backhaul in a technical specification, i.e., a fixed-network backhaul network). In the related art, the fixed network line is located through information such as an outer layer (or local) IP address and port number of the H(e)NB. The information is sent to the PCRF through a flow of User Equipment (UE) attachment from the H(e)NB or of a PDN connection establishment; and the PCRF finds the BPCF in charge of resource control and management of the fixed network line for the H(e)NB, and establishes an S9* session with the BPCF.
According to the related art, a specific flow of handing the UE from a macro-cell over to a micro-cell, or handing the UE over different micro-cells, as shown in FIG. 2, mainly including the following steps:
Step 201, the UE accesses from a source (H)eNB (macro-cell or micro-cell (H)eNB, S(H)eNB), initiates a handover at a certain time, and selects to access from a target HeNB (T-HeNB).
Step 202, the S(H)eNB sends a handover request message to a source MME (i.e., S-MME).
Step 203, the S-MME sends a target MME (i.e., T-MME) a relocation request forwarding message used for delivering context information to a target side and notifying the target side to perform a handover operation.
Step 204, if S-GW relocation occurs, then the T-MME sends a session establishing request message to a target S-GW (i.e., T-S-GW) and receives a session establishing response message from the T-S-GW; if S-GW relocation doesn't occur, i.e., the S-S-GW and the T-S-GW are the same gateway, then the operation of this step is skipped and is not executed.
Step 205, the T-MME sends a handover request message to the T-HeNB, and receives a handover acknowledgement message returned by the T-HeNB; if S-GW relocation occurs in the previous step 204, then it is also required to establish, in step 205, a user plane data channel between the T-HeNB and the T-S-GW.
Step 206, the T-MME sends the S-MME a relocation response forwarding message as a response to the step 203.
Step 207, the S-MME sends a handover instruction to the source (H)eNB, and the source (H)eNB forwards the handover instruction to the UE to notify it to perform the handover.
Step 208, the UE sends a handover confirming message to the T-HeNB, and the UE hands a radio channel over to the target side.
Step 209, the T-HeNB sends a handover notification message to the T-MME.
Step 210, the T-MME and the S-MME exchange a relocation completion notification/acknowledgement forwarding message.
Step 211, if S-GW relocation occurs, the T-MME sends a bearer modifying request message to the T-S-GW, and as a return, the T-S-GW sends a bearer modifying response message to the T-MME; meanwhile, the triggered T-S-GW sends a bearer modifying request message to the P-GW, and the P-GW also returns a bearer modifying response message to the S-S-GW.
If the S-GW relocation doesn't occur, then the T-S-GW is the S-S-GW; only the T-MME and the S-GW exchange the bearer modifying request/response message, and message interaction between the S-GW and the P-GW will not be performed.
Step 212, if the P-GW receives the bearer modifying request message from the S-GW, then the P-GW and the PCRF intercommunicate in an IP-Connectivity Access Network (IP-CAN) session modifying step to update an IP-CAN session; if the P-GW doesn't receive a triggering message or there is no special information which the PCRF is to be notified of in the bearer modifying message received by the P-GW, then the step is omitted.
Step 213, the UE initiates a Tracking Area Update (TAU) operation after completing the handover, and the user updates the mobility management context of the UE in the MME.
Step 214, the S-MME sends a UE context releasing instruction message to the source (H)eNB to release the context of the user at a source network side.
Now, the handover is completed.
By analyzing the above handover steps, the following defects may be seen: 1) the UE has been handed over between micro-cell (H)eNBs, while what the core network has is the outer layer or local IP address/port number of the S-(H)eNB, which will result in a resource control error; 2) the UE is handed from a source macro-cell over to a micro-cell, while the core network side cannot receive information on the local IP address/port number of the fixed network line where the target HeNB is located which will also lead to failure of policy interworking and resource management. The above defects are all caused by a failure to update tunnel information related to the target HeNB at the core network when the UE is handed over between (H)eNBs; and because the tunnel information related to the target HeNB cannot be updated at the core network when the UE is handed over between (H)eNBs, policy interworking between the mobile network and the fixed network cannot be implemented, nor can the QoS of the HeNB be ensured.